Smoking Article Filter

ABSTRACT

A filter for a smoking article comprising first and second sections, the first section being at the mouth end of the filter and comprising a cylindrical element circumscribed by a wrapper and having a hollow portion extending therethrough, and the second section being longitudinally aligned with and adjacent to the first section and comprising a filtration material. The second section comprises a particulate material in a circumferential region and extending to the end of the second section immediately adjacent the first section. Also provided is a smoking article incorporating a filter according to the invention.

The present invention relates to a filter for a smoking article andsmoking articles incorporating a filter element.

Smoking articles, and filters therefore, can vary significantly from onemarket to another as a result of many different factors includingconsumer preference and tradition. In certain markets there is apreference for a filter having a recess at the mouth end, which may beused to lengthen the filter as a whole. The recess is achieved byoverwrapping the plug of filtration material with a plugwrap thatextends beyond the end of the plug of filtration material at the mouthend of the filter. In order to minimise the susceptibility of theoverhanging portion of the plugwrap to damage and deformation, forexample as may result from the packaging process or during handling andsmoking by a consumer, a plugwrap which is thicker than a conventionalcigarette plugwrap is used. Such a plugwrap has up to four times thebase weight of a conventional plugwrap and thus is significantly moreresistant to deformation and adds a high level of rigidity at the mouthend of the filter. However, the need for such a thick plugwrap meansthat conventional (more economical) plugwraps cannot be used on filtershaving a recessed end and also add significant problems to the processof ventilating the filter, and in particular to the process of onlinelaser perforation of the filter, thus not allowing high levels ofventilation to be attained.

Various known filter arrangements are disclosed in GB2203324; GB2170695;GB 2150415; GB 2150413; GB 2135865; GB 0781654; WO 99/65343 and U.S.Pat. No. 3,396,733.

The present invention provides a filter for a smoking article comprisinga first and a second section, the first section being at a mouth end ofthe filter and comprising a cylindrical element having a hollow portionextending therethrough and being circumscribed by a wrapper, and thesecond section being longitudinally aligned with and adjacent to thefirst section and comprising a filtration material. The second sectioncomprises a particulate material in a circumferential region thereof,the particulate material extending to the end of the second sectionimmediately adjacent the first section.

The use of particulate materials, such as carbon or activated carbon, intobacco smoke filter elements to reduce vapour phase constituents ofsmoke has been known for some while. A known way of including carbon orother additives in filters is to adhere particles of the additive to awrapper surrounding the filter element. GB 2,260,477 and GB 2,261,152describe various configurations of additive adhesion. In somecircumstances, particulate carbon, when provided in a mouth end filtersection, may be liable to fall out of the end of the filter. This ishighly undesirable as it is possible that particulate carbon may becomeloose and enter the mouth of the consumer. The provision of a firstfilter section at the mouth end of the filter having a hollow portionextending therethrough helps to prevent the fall out of the particulatematerial whilst maintaining the appearance of a recessed filter.

The particulate material may extend over the full longitudinal length ofthe second section. The particulate material may also extend over thefull width of the wrapper. In this instance the particulate material maycover the entire surface of the wrapper, although a seam may be leftuncovered to allow adhesive to be applied and the wrapper to be sealedabout the filtration material. Alternatively, the particulate materialmay extend over only a portion of the longitudinal length of thewrapper. Similarly, the particulate material may extend over only aportion of the width of the wrapper.

The particulate material may extend over two or more portions of thesecond section. The two or more portions are preferably spacedcircumferentially from one another.

Alternatively, the two or more portions may comprise three, four, five,six, seven or eight portions.

In some embodiments, the filtration material of the second section mayfurther comprise a particulate material interspersed in the filtrationmaterial.

The particulate material of the filtration material may be the same asthe particulate material provided at the circumferential region of thesecond section of the plugwrap. Alternatively, the particulate materialof the filtration material may be different from the particulatematerial provided at the circumferential region of the second section ofthe plugwrap.

In some embodiments, the wrapper may further comprise ventilation means.For example, the ventilation means may comprise one or more ventilationholes provided in gaps between the two or more portions.

The cylindrical element will generally have a thickness (in the radialdirection) sufficient to occlude at least part of the particulatematerial. In other words, the cylindrical element acts as a physicalbarrier located at the mouth end of the particulate material to preventthe particular material from escaping from the second section of thefilter. The thickness of the cylindrical element may be from 1-4 mm, andis preferably in the range 1-3 mm.

Suitably the cylindrical element is circumscribed by a wrapper, which ispreferably a plugwrap. This plugwrap may have a base weight of less than50 g/m², less than 45 g/m², less than 40 g/m², less than 35 g/m², lessthan 30 g/m². This plugwrap may have a base weight equivalent to aconventional plugwrap (wrapper), namely approximately 23 toapproximately 27 g/m².

A second aspect of the present invention provides a smoking articlecomprising a filter according to the invention.

Preferably the particulate material includes sorbents (e.g. selectedfrom activated carbon, charcoal, silica gel, sepiolite, alumina, ionexchange material etc.), pH modifiers (e.g. alkaline materials such asNa₂CO₃, acidic materials), flavourants, other solid additives andmixtures thereof.

Advantageously the particulate material is selected from a group ofrelatively high surface area materials capable of adsorbing smokeconstituents without a high degree of specificity. Suitable generaladsorbents can be selected from the group consisting of carbon,activated carbon, activated charcoal, activated coconut carbon,activated coal-based carbon or charcoal, zeolite, silica gel,meerschaum, aluminium oxide (activated or not), carbonaceous resin orcombinations thereof.

An example of a suitable coal-based charcoal is one made fromsemi-anthracite coal with a density about 50% greater than coconut-basedcharcoal (available from Calgon Carbon, Pittsburgh, Pa., WA).

An example of a suitable carbonaceous resin is one derived from thepyrolysis of sulphonated styrene-divinyl benzene, such as Ambersorb 572or Ambersorb 563 (available from Rohm and Haas). To enhance theefficiency of the general adsorbent metal oxides or other metal basedcomplexes may optionally be included in or impregnated on the generaladsorbent section.

In one embodiment, preferably the particulate material used herein iscarbon, for instance activated carbon, or charcoal or other absorbentmaterial. In one embodiment, preferably the activated carbon isactivated coconut carbon.

Any particulate material used may be a single substance or a mixture,and/or may be in admixture with other material.

In one embodiment preferably the particulate material is disposed in twoseparate regions spaced circumferentially from one another.Alternatively, the particulate material may be disposed in 3, 4, 5, 6, 7or 8 separate regions each spaced circumferentially from one another.Further, a greater number of regions may be used if required.

Each separate region or portion of particulate material may be comprisedof particulate material which is the same as or different from the otherseparate regions. In one embodiment preferably the particulate materialin the separate regions is the same.

In one embodiment, suitably the particulate material may be applied totwo or more portions of the longitudinal inner face of the wrapper.

In one embodiment the particulate material is disposed around the innercircumference of the wrapper such that the wrapper has an overlappinglongitudinal edge which is free of said particulate material and whichprovides a lapped and stuck seam holding the wrapper around the core.

The particulate material may extend continuously over the fulllongitudinal length of said wrapper. By continuously it is meant thatthe particulate material is applied such that the loading at any onepoint on the longitudinal length of the wrapper is the same (orsubstantially the same) as the loading at any other point on the samelongitudinal length of the wrapper. By continuously it is meant that atno point along the longitudinal length of the wrapper is there a portionof the wrapper without particulate material if the particulate materialis present at another point along the same longitudinal length of thewrapper. Preferably, the particulate material is applied longitudinallyto the wrapper (e.g. plugwrap) in a continuous manner. Preferably alongthe longitudinal axis of the wrapper the particulate material is presentas a continuous stream (i.e. without breaks or spaces). In other words,the particulate material extends in a continuous manner along thelongitudinal axis of the wrapper.

The particulate material may extend continuously over the full width ofsaid wrapper.

In some embodiments the particulate material may be present as patches.

The wrapper of the filter element is preferably a paper wrapper.Preferably the wrapper is a conventional plugwrap.

In one embodiment the wrapper may be a conventional plugwrap whichcovers 360° of the core, in which case the plugwrap has a lapped andstuck seam holding the wrapper around the core.

In one embodiment, preferably the filter element according to thepresent invention has a filtration material comprising particulatematerial interspersed with the filtration material and has a plugwrapwhich covers 360° of the filtration material.

In another embodiment the wrapper (in particular plugwrap) preferablydoes not extend 360° around the filtration material. In other words, inone embodiment preferably the wrapper is a split wrapper. A splitwrapper is one which extends circumferentially about the filtrationmaterial, but extends less than 360° around the circumference of thefiltration material. In such an embodiment, there is not lapped andstuck seam holding the wrapper around the filtration material. Instead,the split wrapper may be held in place by other known means, such as bybonding the wrapper directly to the filtration material for instance.

The wrapper for use in the filter element may be porous or non-porous.

The wrapper for use in the filter element may be ventilated orunventilated.

Advantageously the filtration material of the second section maycomprise (or consist of) conventional fibrous cellulose acetate,polypropylene or polyethylene material or gathered paper material.

Preferably the filtration material comprises cellulose acetate.

In one embodiment, the filtration material of the second section is aDalmatian-type filter material.

The particulate material may be interspersed throughout the filtrationmaterial. Alternatively, the particulate material may be interspersed insome parts (but not all) of the filtration material. The parts may beevenly or unevenly distributed.

The particulate material adhered to the wrapper may be homogenous—in thesense that it is made up of substantially the same component (for someembodiments, preferably all of the same). Alternatively, the particulatematerial adhered to the wrapper may be heterogeneous—in the sense thatit is made up of two or more different components. The particulatematerial adhered to the wrapper may be in contact with the filtrationmaterial. Preferably, some or all of the particulate material adhered tothe wrapper is in contact with the filtration material. For someembodiments, preferably substantially all of the particulate materialadhered to the wrapper is in contact with the filtration material.

The filter is preferably interattached with a smokable filler (e.g.tobacco) rod by way of a tipping wrapper. Advantageously the tippingwrapper is a paper.

In one embodiment the filter may comprise additional filter section(s).The additional filter section(s) will be at the tobacco rod end of thefilter. Suitably, one, two, three or more additional filter sections maybe provided in the filter. The additional filter section(s) may be anytype of filter section known to those skilled in the art. Suitably thefilter sections are arranged longitudinally of one another with the endof each filter element abutting the next.

Suitably the wrapper surrounding the second section of the filter ispreferably pre-coated with the particulate material.

The particulate material may be adhered to the wrapper by hot meltadhesive (e.g. various polyester adhesives), high m.p. polyethyleneglycol, or emulsion-type adhesive such as PVA.

The particulate material may be directly or indirectly adhered to thewrapper. An example of direct adherence is wherein the particulatematerial is affixed to the wrapper (such as the inner surface thereof)by means of a suitable adhesive. An example of indirect adherence iswherein the particulate material is affixed to an intermediate layer(which may be made of paper or other suitable support matrix—such as atextile material—or combinations thereof) by means of a suitableadhesive and wherein the intermediate layer is affixed to the wrapper(such as the inner surface thereof) by means of a suitable adhesive.

Suitably the additional filter section(s) of the filter may be comprisedof conventional fibrous cellulose acetate, polypropylene or polyethylenematerial or gathered paper material. The additional filter section(s)may optionally comprise one or more additives, for instance disposedupon or within the material of the filter element may be furtherflavouring materials, as described above, which are released or elutedfrom the filter element during use.

The cylindrical element of the first section at the mouth end may bemade from a variety of materials, for example, cellulose acetate tow,cellulose, paper, cotton, polypropylene web, polypropylene tow,polyester web, polyester tow or combinations thereof. It is preferredthat the element comprises cellulose acetate.

In addition, the pressure drop and/or mechanical filtration efficiencyof the filter sections can be selected to achieve the desired smokingmechanics and filtration characteristics as may be required with thespecific product design desired.

A part of the filter may comprise a catalyst. Advantageously thecatalyst facilitates the conversion of carbon monoxide (CO) to carbondioxide (CO₂) in the vapour phase of the smoke. It is much by preferencethat the catalyst is highly selective for carbon monoxide. Suitably thecatalyst may be one of the group consisting of transition metal oxides,silica, alumina, zeolites, impregnated carbon, for example, carbonimpregnated with metals.

Suitably the filter and/or smoking article according to the presentinvention may comprise ventilation means. For example, the ventilationmeans may comprise one or more holes in the wrapper engaged around thefiltration material of the second section. The holes may advantageouslybe positioned in regions of the wrapper to which the particulatematerial is not adhered. Ventilation holes are often formed in filterwrappers by laser piercing. Carbon granules in the region whereventilation is required can cause the laser to produce sparks when theholes are being made. Positioning the ventilation holes in gaps betweenthe portions of particulate material addresses this problem.

The ventilation means may comprise perforation holes in the tippingwrapper used to interattach the filter and the rod of wrapped smokablefiller (e.g. tobacco) material.

Alternatively the ventilation means may be provided by the use of aporous tipping wrapper used in conjunction with a perforated plugwrap.The porous tipping wrapper may be porous over its full extent or overonly a localised extent, which extent is in registration with theunderlying perforated plugwrap.

The ventilation means may further be provided at or close to the end ofthe rod of wrapped smokable filler (e.g. tobacco) material. Theventilation means may be provided in the tipping wrapper or in thecigarette paper wrapper enwrapping the smokable filler (e.g. tobacco)material.

Suitably, the filter may be attached to a wrapped smokable fillermaterial rod (i.e. a wrapped tobacco rod for instance) by conventionaltipping overwrap to form a smoking article. The tipping overwrap may beventilating or non-ventilating overwrap.

The length of the smoking material rod is advantageously at least 60 mmand the rod should preferably yield not less than six puffs, and morepreferably not less than seven puffs when smoked under standard machinesmoking conditions. The rod is preferably of uniform cross-sectionalshape and dimensions throughout the length of the rod.

The wrapper enwrapping the smoking article may comprise a burn additive,such as sodium and/or potassium citrate, for example. Other suitableburn additives, such as sodium or potassium salts, such as acetate andtartrate; mono-ammonium phosphate, and di-sodium hydrogen phosphate, forexample, will be known to the skilled man. The burn additive may bepresent in the range of 0.5-2.5% by weight of the wrapper. The wrappermay also have a base weight in the range of 20-40 g/m².

The wrapper of the smoking article may alternatively or in addition be anon-paper wrapper, such as the wrappers described in InternationalPatent Applications, Publications Nos. WO 96/07336 and WO 01/41590. Suchwrappers assist in the reduction of sidestream smoke components, butstill provide a smoking article which has burning and ashingcharacteristics similar to conventional products, i.e. the wrappersallow the smoking article to burn down and ash in a similar way toconventional products.

Suitably, the smokable filler material may be tobacco-containingmaterial or a tobacco substitute material. Preferably the smokablematerial is a tobacco material. Suitably the tobacco material comprisesone or more of stem, lamina, tobacco dust and reconstituted tobacco. Itis preferred that the tobacco material comprises one or more of thefollowing types: Virginia or flue-cured tobacco, Burley tobacco,Oriental tobacco, reconstituted tobacco. It is much by preference thatthe smokable material comprises a blend of tobacco material.Advantageously the smokable material comprises 10-80% Virginia tobacco,10-60% Burley tobacco, 0-20% Oriental tobacco, 0-120% reconstitutedtobacco and 0-30% expanded tobacco.

The term ‘carbon’ as used herein can be taken to cover a material whichis substantially solely carbon and any carbon precursors, such ascarbonaceous material. As used herein the term carbonaceous includesmaterial which has been pyrolysed, which material preferably containscarbon, although some incomplete combustion products may still bepresent. Ready pyrolysed coconut fibre may, for example, be thecarbonaceous material from which carbon is derived.

As used herein, the term ‘smoking material’ or ‘smokable fillermaterial’ means any material which can be used in a smoking article. Itdoes not necessarily mean that the material itself will necessarilysustain combustion.

As used herein, the term ‘smoking article’ means any product that isused in the tobacco industry and includes smokable products or similarproducts for delivering an aerosol to the consumer. Smoking articlesinclude cigarettes, cigars, cigarillos and similar articles.

In order that the present invention may be clearly understood andreadily carried into effect reference will now be made, by way ofexample, to the accompanying drawings in which:

FIG. 1 shows a longitudinal cross-sectional view of a filter having arecess at the mouth end according to the prior art;

FIG. 2 shows a longitudinal cross-sectional view of a filter accordingto one embodiment of the present invention;

FIG. 3 shows an end view from the mouth end of a filter according to oneembodiment of the present invention;

FIG. 4 shows a longitudinal cross-sectional view of a filter accordingto a further embodiment of the present invention; and

FIG. 5 shows a longitudinal cross-sectional view of a tilter accordingto an alternative arrangement of the present invention.

FIG. 1 shows a known filter 1 attached to a tobacco rod 2 (only aportion of which is shown) to form a cigarette. Filter 1 consists of aplug of cellulose acetate 3 (filtration material) circumscribed by aplugwrap 4. The plugwrap 4 is longer than the plug of cellulose acetate3 and overhangs the plug of cellulose acetate at the mouth end of thefilter 1 to create a recess having a depth typically of approximately 5mm. The length of overhang of the plugwrap 4 is designated in FIG. 1 bythe reference character x. The filter 1 is attached to the tobacco rodby a tipping wrapper 5 in the conventional manner. The plugwrap 4 istypically a wrapper having a high base weight, for example 100 g/m² toprovide rigidity to the filter 1.

FIG. 2 shows a filter 1 in accordance with the present invention inwhich a first section at the mouth end of the filter 1 comprises atubular plug of cellulose acetate 6 having a hollow central core,designated by reference numeral 7 in FIG. 2. The filter 1 also consistsof a second section at the tobacco rod end of the filter 1 and adjacentthe first section. The second section comprises a plug of celluloseacetate filtration material 3 circumscribed by a plugwrap 4, whichplugwrap 4 may also circumscribe the cellulose acetate plug 6 of thefirst section. Alternatively the plugs 3, 6 may each be circumscribed bya respective individual plugwrap. The filter 1 is attached to a tobaccorod 2 to form a cigarette by a standard tipping wrapper 5. The plugwrap4 and/or the tipping wrapper 5 may be ventilated (not shown) at anypoint over their surface and to a varying amount dependent on theparticular product. The plug of cellulose acetate 6 of the first filtersection may for instance be 7 mm in length and provides rigidity to themouth end of the filter 1 and allows a conventional plugwrap 4 to beused without reducing strength.

FIG. 3 shows the filter of FIG. 2 in end view from the mouth endthereof. The cylindrical plug of cellulose acetate 6 defines a hollowcore 7 longitudinally along the centre of the plug 6. The plug ofcellulose acetate filtration material 3 of the second section can beseen at the far end of the hollow core 7. The thickness of thecylindrical plug of cellulose acetate 6 is defined by the outer surfaceof the plug 9 and by the inner surface of the plug 8. This thickness,designated by reference character z in FIG. 3, may vary depending on thedesired size of the recess at the mouth end of the filter 1. Thecylindrical plug of cellulose acetate 6 is circumscribed by a plugwrap(not shown) and is surrounded by a tipping wrapper (not shown) to jointhe filter 1 to a tobacco rod in a formed cigarette. The inner-surfaceof the plug of the first filter section may be of any desired shape andthus serve to create a recognizable shape for the hollow core 7.

The filter 1 of FIG. 4 comprises all of the features of FIG. 2, and samereference numerals are used to denote equivalent features, with theaddition of a particulate activated carbon 10 adhered to the innersurface of the plugwrap 4 circumscribing the plug of cellulose acetate 3of the second filter section. The carbon 10 extends the entirelongitudinal length of the second section, being for instance 20 mm inlength. The thickness of the wall of the plug of cellulose acetate ofthe first filter section is sufficient to cover the carbon at theposition of abutment between the first and second filter sections andprevent any carbon 10 becoming loose and escaping into the first filtersection or beyond the mouth end of the filter 1.

FIG. 5 shows a filter 1 which comprises all of the features of FIG. 4,with the alteration in the length of the layer of carbon 10. Particulateactivated carbon 10 extends over only a portion of the plugwrap 4 whichcircumscribes the plug of cellulose acetate 3 of the second filtersection. The carbon 10 extends from the end of the plug of celluloseacetate 3 nearest the mouth end of the filter 1 to a position part wayalong the plug 3 towards the tobacco rod 2.

All publications mentioned in the above specification are hereinincorporated by reference. Also included herein by reference is ourco-pending UK patent application filed on 6 Jul. 2006 and havingapplication number 0613483. Various modifications and variations of thedescribed methods and system of the present invention will be apparentto those skilled in the art without departing from the scope of thepresent invention. Although the present invention has been described inconnection with specific preferred embodiments, it should be understoodthat the invention as claimed should not be unduly limited to suchspecific embodiments. Indeed, various modifications of the describedmodes for carrying out the invention which are obvious to those skilledin the art are intended to be within the scope of the following claims.

1. A filter for a smoking article comprising a first and a secondsection, the first section being at a mouth end of the filter andcomprising a cylindrical element having a hollow portion extendingtherethrough and being circumscribed by a wrapper, and the secondsection being longitudinally aligned with and adjacent to the firstsection and comprising a filtration material, wherein the second sectioncomprises a particulate material in a circumferential region thereof,the particulate material extending to an end of the second sectionimmediately adjacent the first section.
 2. The filter according to claim1, wherein the particulate material extends over a full longitudinallength of the second section.
 3. The filter according to claim 1,wherein two or more portions of the circumferential region of the secondsection comprise particulate material.
 4. The filter according to claim3, wherein the two or more portions are spaced circumferentially fromone another.
 5. The filter according to claim 4, wherein the two or moreportions are arranged symmetrically around the second section.
 6. Thefilter according to claim 1, wherein a wrapper surrounds the secondsection and the particulate material is adhered to a surface of thewrapper.
 7. The filter according to claim 6, wherein the particulatematerial is adhered to an inner surface of the wrapper surrounding thesecond section.
 8. The filter according to claim 1, wherein theparticulate material is an adsorbent.
 9. The filter according to claim8, wherein the particulate material is activated carbon.
 10. The filteraccording to claim 1, wherein the second section further comprises aparticulate material interspersed in the filtration material.
 11. Thefilter according to claim 1, wherein the cylindrical element has a walldefined by the outer surface of the element and the hollow portionextending therethrough, the wall being of a thickness to at least partlyocclude the particulate material in a circumferential region of thesecond section at the point of abutment of the first and secondsections.
 12. The filter according to claim 1, wherein the wrappercircumscribing the first section is a plugwrap.
 13. The filter accordingto claim 12, wherein the plugwrap has a base weight of less than 50g/m².
 14. The filter according to claim 1, wherein the cylindricalelement of the first section comprises cellulose acetate.
 15. The filteraccording to claim 1, further comprising at least one additional filtersection at the tobacco rod end of the filter.
 16. The filter accordingto claim 1 wherein two or more portions of the circumferential region ofthe second section comprise particulate material, and the two or moreportions are spaced circumferentially from one another, wherein awrapper surrounds the second section and the particulate material isadhered to a surface of the wrapper, and the particulate material isadhered to an inner surface of the wrapper surrounding the secondsection.
 17. The filter according to claim 1 configured as a componentwithin a smoking article.